Technical Field
This Patent Disclosure relates to touch input, such as for use in mobile/personal communications/computing devices.
Related Art
In mobile devices (and other equipment), touch sensing technology can be used to replace physical/mechanical buttons. Touch sensing, which can be based on capacitive and inductive sensing, can be used to detect touch deflection/deformation of a touch button defined on a touch surface.
In the case of inductive touch sensing, a sense coil (inductor) is driven to project a time-varying magnetic sensing field within a defined sensing area that can encompass a touch surface area spaced from the sensor. The magnetic sensing field induces eddy current loops in the proximate touch area, resulting in an eddy-current back emf (electromotive force) voltage opposing the sensor-projected sensing field, and eddy-current energy losses (resistive) in the touch area.
Eddy current sensing can be based on changes in mutual inductance between the sense coil and the induced eddy current loops resulting from the back emf/voltage induced in the sense coil inductor, and/or changes in sensor impedance resulting from the resistive energy loss in the touch-area eddy current loops. Changes in mutual inductance can be measured/detected based on, for example, changes in sensor inductance, or changes in a sensor property corresponding to inductance. Changes in sensor impedance reflecting resistive energy loss can be measured/detected based on, for example, changes in the signals that drive the sensor to project the sensing field.